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character: Circulatory System Overview
topic: The circulatory system is responsible for transporting blood, nutrients, gases, and waste products throughout the body. It consists of the heart, blood vessels, and blood.
topic: Arteries have thicker, more muscular walls to handle high-pressure blood flow, whereas veins have thinner walls and often contain valves to prevent backflow.
topic: Arterial blood is typically bright red due to high oxygen content, while venous blood is darker red due to a higher concentration of carbon dioxide.